How Many Solar Attic Fans Do I Need?

How many solar attic fans you need depends on factors such as the size of the attic space, capacity, fan power consumption, and the roof pitch. Considering all these factors, you can accurately estimate the solar-powered attic fans you need.

A solar attic fan may sound strange to some individuals, but it only amplifies the beauty of the diversity of solar products utilized in homes, factories, and offices. The attic space is one of the most neglected places in the house. Most times, when the house is very hot, you may wonder where the heat is coming from. The hot air in your attic is responsible for the increased temperature in your home. The solution will be attic ventilation, and this is where the solar-powered attic fan comes in.

What’s a Solar Attic Fan?

This solar fan is an electrical piece of equipment that functions like a roof exhaust, dispelling hot air from the attic space and inviting cool air to circulate through the attic space. This equipment is solar-powered, so it comes with a solar panel responsible for powering the fan. This solar fan is installed on the roof – whether flat or steep and the solar panels tap energy from direct sunlight and convert it into electricity for the fan blades.

The functionality of the solar attic fan depends on gravity. This is because solar attic fans work by driving out the heat in the attic. Despite its modest popularity, there’s a huge market for attic fans. As of 2021, it was valued at $6.1 billion.

The Advantages of Using Solar-powered Attic Fans


Like other solar equipment, solar attic fans incur little to no expenses after their installation. As long as nothing breaks, you won’t have to do any maintenance unless you want to count cleaning the solar panels twice a year. More importantly, solar attic fans don’t add more costs to your electricity bill because it sources their electricity from direct sunlight.

Good for Managing Heat in the Summer

The summer season typically comes with so much heat. In some places, the temperatures can soar to 130°F. This will make the house unbearably hot and result in attic humidity, which can damage things stored in the attic over time. Having these fans installed on your roof will ensure proper ventilation in the attic, effectively lowering the temperature by inviting cold air into the house.

It Doesn’t Take Cold Air From other Parts of the House

Unlike some ventilation equipment that draws cold air from other places in the house and overworks the air-conditioner, solar attic fans source ventilation from the environment.

No Need to Hire an Electrician

man installs solar attic fan

This is another advantage that makes solar attic fans a cost-effective ventilation option. When you purchase a solar attic fan, you only need to install it on your roof. You don’t need to pay an electrician for any wiring.

Safe for the Home

With solar attic fans, there’s no absolutely no risk of a fire hazard in the house. On the flip side, conventional attic fans can trigger electric fires if their wires are faulty. Also, solar attic fans don’t pull toxic emissions from nearby equipment into the attic – something electric-powered attic fans can do.

No Noise

Unlike electric-powered attic fans that are noisy when switched on, solar attic fans offer peace and quiet.

Environmentally Friendly

Aside from their quietness, solar attic fans tap and use renewable energy from the sun to function. They don’t emit greenhouse gases such as carbon monoxide into the environment. Using solar attic fans reduces your carbon footprint in the environment. There’s no noise pollution or air pollution.

Visually Appealing

Solar-powered attic fans are sleekier than their electric-powered counterparts and are less distracting. They also look better on the roof.

Reduces Humidity in the Attic During the Winter Season

Snowfall during winter can result in dampness, moisture, water damage, duct corrosion, and other significant issues in the attic space. Solar attic fans expel the humid air out and bring dry air in, significantly reducing the damage that ice damming could cause.

How Many Solar Attic Fans Do I Need – The Factors That Will Help You Determine It

Without these factors, you’ll be in the dark regarding how many solar fans you need. They include;

Air-Venting Capacity

The capacity of a solar attic fan is measurable in CFM (cubic feet per minute), which refers to how much air a fan can circulate under optimal working conditions. In practical applications, it’s very difficult to replicate the exact CFM, but you can get something close to it.

Solar Panel Rating

Though this largely depends on the size of your attic area, it also determines how many solar-powered attic fans you’ll need to install. A common rating is 20 watts.

Attic Size

The number of solar attic fans should be proportional to the size of your attic space, which is measurable in square feet. To calculate the attic size, you should get the length and breadth of the house and multiply it. The larger the square footage, the more fans you’ll need. For example, an attic size of 1,000 ft² will need fewer solar attic fans than a square footage of 800 ft².

The Roof Pitch

This refers to the steepness or flatness of your roof. It can be measured by x/12; x represents the value of the roof slope. The roof entails describes how much the roof rises per 12 feet. A very flat roof will have a pitch of 2/12, meaning the roof just rises 2 feet across a space of 12 feet. On the flip side, a very steep roof can be 12/12, meaning the roof rises to a 45-degree angle. The flatter the roof, you’ll need fewer attic fans, and vice versa. Some roofs are between – 5/12 and 8/12. It’s important to note that steeper roofs come with vaulted ceilings.

The Presence or Absence of Air Vents

As you already know, a solar attic fan draws hot air out and brings cold air into the attic. However, you didn’t know that for attic ventilation to be more effective, there should be air intake vents. Homes with soffit vents on the edge of the roof will work well with attic fans. If your home doesn’t have a soffit vent installation, we recommend having it done. Ensure you have 4ft² of these vents per solar fan.

Peak Sunlight Hours

The more sunlight in your area of residence, the more energy your solar fan will receive to keep working. Southern states in the US are known to be warmer than their northern counterparts.

Hybrid Fans

Hybrid attic fans combine the qualities of a solar-powered and an electric-powered fan. It uses solar energy to power the fans during the day when the sun is shining, then gets power from the grid when the sun sets. With hybrid fans, you may need fewer solar attic fans. However, these fans will increase your electricity bill since they use electricity when there’s no solar power to make the fans work.

Below are images showing a tabular representation of how many fans you’ll need based on the attic size and slope of the roof. For the fan wattage, we’ll be going with 20 watts.

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